This invention relates to an improvement in a system for the production of an ether wherein an olefin-containing feed stream is catalytically etherified with an alcohol, and the product formed during etherification is distilled into: an overhead fraction of unreacted, light hydrocarbons and unreacted alcohol, and a bottoms fraction of the desired ether. The overhead fraction is then condensed, and the alcohol is thereafter separated from this condensate.
Suitable additives for gasoline include, besides the conventional methyl tert-butyl ether, higher tertiary ethers as well, an example being the tert amyl homolog. The purpose of adding ether is primarily to raise the octane number of the fuel. The ethers are produced by selective catalytic etherification of the corresponding olefinic fractions with alcohol especially methanol.
In a conventional method of this type (Chemical Engineering Progress, August 1982, pages 36-45), a C.sub.5 hydrocarbon feed stream is mixed with methanol and introduced into the reactor in a presence of a selective catalyst to convert a fraction of the feedback to tertiary amyl methyl ether (TAME). The reaction mixture discharged from the reactor, containing hydrocarbons, ether and methanol, is thereafter introduced into a distillation column to separate the methanol by azeotropic distillation whereby there is obtained an overhead fraction containing the unreacted methanol as well as part of the unreacted C.sub.5 hydrocarbons, and a bottoms product containing the TAME as well as the remaining unreacted C.sub.5 hydrocarbons. The methanol in the overhead is separated from the C.sub.5 hydrocarbons by a water scrubbing step, and the water is thereafter separated from the methanol in a distillation column.
In this process, the separation of unreacted methanol, requiring both a water scrubbing step and a methanol/water distillation step, is relatively expensive.